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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
namespace AK {
struct DefaultComparator {
template<typename T, typename S>
constexpr int operator()(T& lhs, S& rhs)
{
if (lhs > rhs)
return 1;
if (lhs < rhs)
return -1;
return 0;
}
};
template<typename Container, typename Needle, typename Comparator = DefaultComparator>
constexpr auto binary_search(
Container&& haystack,
Needle&& needle,
size_t* nearby_index = nullptr,
Comparator comparator = Comparator {}) -> decltype(&haystack[0])
{
if (haystack.size() == 0) {
if (nearby_index)
*nearby_index = 0;
return nullptr;
}
size_t low = 0;
size_t high = haystack.size() - 1;
while (low <= high) {
size_t middle = low + (high - low) / 2;
int comparison = comparator(needle, haystack[middle]);
if (comparison < 0)
if (middle != 0)
high = middle - 1;
else
break;
else if (comparison > 0)
low = middle + 1;
else {
if (nearby_index)
*nearby_index = middle;
return &haystack[middle];
}
}
if (nearby_index)
*nearby_index = min(low, high);
return nullptr;
}
}
using AK::binary_search;
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